Controlling the spatial arrangement of π-conjugated groups or π-conjugated molecules is an extremely important matter in the field of organic material development. In other words, the spatial interactions between π-conjugated groups or π-conjugated molecules has an effect on the optical properties, electrical properties, electrochemical properties or the like of organic materials, including the excimer emission and charge transfer of the material within solution or within a solid state.
By controlling the spatial arrangement to achieve a certain aligned arrangement of the π-conjugated groups or π-conjugated molecules, organic materials can be obtained that have favorable optical properties, electrical properties, electrochemical properties or the like that can be used within field effect transistors (FET), light emitting diodes (LED), solar cells, chemical sensors, biosensors, laser materials or the like. For this reason, molecular design and synthesis aimed at controlling the orientation and arrangement of π-conjugated groups or π-conjugated molecules by using methods of controlling molecular crystals, self-assembly and supramolecular chemistry has been the subject of active research. However, free arrangement and orientation of π-conjugated groups or π-conjugated molecules is still a distant goal.
On the other hand, three dimensional spatial control of polymer materials is attracting much attention as an effective means of controlling the arrangement of π-conjugated groups or π-conjugated molecules. A number of examples have been reported.
In the case of straight-chain polymers having π-conjugated groups within the main chain, the following reports have been disclosed regarding structures in which π-conjugated groups are stacked (π-stacked structures) and structures in which straight-chain polymers adopt a repeating folded structure.
Non-Patent Literature 1 discloses that an oligomer having perylene tetracarboxylic acid diimide as the π-conjugated groups, with these groups linked by comparatively long linking portions, adopts a repeating folded structure in solution. With this oligomer, a stabilized structure is obtained in which the perylene tetracarboxylic acid diimide groups that represent the π-conjugated groups adopt a continuous stacked structure (π-stacked structure).
Further, Non-Patent Literature 2 and Non-Patent Literature 3 disclose that tertiary diarylurea oligomers preferentially adopt a repeating folded structure within solution.
On the other hand, in relation to these reports, Non-Patent Literature 4 and Patent Literature 1 have reported examples of polymers that adopt a π-stacked structure in which the arrangement of substituent groups (pendants) bonded consecutively to the polymer main chain are controlled. In these Literatures, it was determined that in polymers prepared using 1,1-dibenzofulvene or a derivative thereof as a monomer, by selecting an appropriate polymerization method, the fluorene groups bonded consecutively to the polymer main chain folded and adopted a stacked arrangement. In this type of polymer, a shortening of the ultraviolet absorption wavelength and a lengthening of the fluorescence emission wavelength are observed as a result of the folding and stacking of the fluorene groups. Moreover, charge transfer measurement by laser excitation in the solid state confirms a high-speed charge transfer.